The determination of attachment of an object to a specific group is provided on the base of studying the sings of an object and comparing them with sings of other objects of the same class (group).
During the analysis of criminalistics literature and criminalistics methods, we found out that scientists and practicians determine two main features in objects that we provisionally call the results of an engineer-technical activity of a person: the purpose and suitability. Analyzing these concepts we can make a conclusion that the purpose is the correspondence of the first plan to general principles of construction of devices of special type and the suitability — is the degree of realization of that first plan.
At the end we come to a conclusion that in the base of group identification of objects that are the results of an engineer-technical activity of a person, can be the analysis of two main stages of their creation: of the development (an aim, project, calculations, designing) — the purpose of an object and realization (the conformity of real-time device characteristics to characteristics that are formed on the phase of development and that are typical to the group of devices of certain type)- its suitability.
Since the expertʼs conclusion is one of the sources of evidence, according to the law it must be assessed by the investigator and the court. In order to correctly use in the evidence the facts established by the forensic expert, the investigator and the court must analyze the content of the entire expertʼs conclusion, and not just his conclusions. The most difficult part for evaluation by the investigation (court) is the research part of the conclusion, describing the progress of the research and its results, in which used scientific methods and techniques are indicated. One of the main points that are evaluated is the scientific validity of the expertʼs conclusions.
It is established that the scientific validity of the expertʼs conclusions is determined, in particular, by the correctness of conducting expert experiments. When carrying out research of the group identification of objects that are the results of engineer-technical activities of a person, to determine the suitability of such objects for certain actions and determine the technical characteristics that determine the qualitative characteristics of these objects (these technical characteristics are used later to determine the purpose of these objects) in most cases during the experiment it is necessary to reproduce the usual way of using of these objects. In exceptional cases, an indirect determination of the necessary technical characteristics is allowed; while preliminary (at the stage of creating the methodology) expert experiments should establish the possibility of such an indirect definition.